1. Field
The invention relates in general to electronics systems and, in particular to power management in electronics systems.
2. Related Art
Electronics systems are frequently comprised of multiple devices. It is often advantageous to have an automatic system for turning on power or turning off power to multiple devices in a predetermined sequence for functional purposes or for reliability considerations. Conventional power sequencing circuits employ centralized control circuitry to turn on power for a first device, then waits for a specified amount of programmed delay time before it turns on power for a second device and so on. Power off sequencing is done in the same manner typically in a reverse order to the power on sequencing. Each device requires its own connection with the centralized controller making system reconfiguration or expansion cumbersome. In a distributed power sequencing approach, each device includes sequencing logic circuit to participate in providing power sequencing function with the centralized control circuitry in a coordinated manner. The communications among the central control circuitry and each of the sequencing logic circuit on these participating devices are accomplished via signals in a sequencing network. The flexibility and expandability of the power sequencing function to support reconfiguration or expansion of the electronics system is limited by available signals in the sequencing network. Accordingly, there is a need for an improved system and method to accomplish the power sequencing function of a large electronics system with minimum number of signals in the sequencing network without compromising the flexibility and expandability.